A silicon oxide film (SiO2 film) and a silicon nitride film (SiN film) are well known as insulating films of a semiconductor integrated circuit device. The SiN film has a specific permittivity higher than that of the SiO2 film and can take an etching selection ratio with respect to the SiO2 film or silicon (Si). For this reason, the SiN film is used at a portion where a permittivity higher than that of the SiO2 film is needed, or is used as an etching stopper layer for the SiO2 film or Si or as a hard mask layer used in processing the SiO2 film or Si.
A film forming apparatus used in manufacturing a semiconductor integrated circuit device is generally classified into a single type film forming apparatus for processing wafers one by one and a batch type film forming apparatus for processing a plurality of wafers at a time. The batch type film forming apparatus includes a vertical batch type film forming apparatus capable of processing a larger number of wafers at a time. The film forming temperature when the SiN film is formed using the vertical batch type film forming apparatus is about 630 degrees C. to 760 degrees C.
Meanwhile, miniaturization of the semiconductor integrated circuit device is further advanced. In a process of manufacturing the semiconductor integrated circuit device, a process at low temperature is required to achieve the miniaturization of the semiconductor integrated circuit device.
In order to form the SiN film at low temperature, a nitriding agent contained in a nitride gas, for example, ammonia (NH3), is used as an active nitride species such as ammonia radicals by using plasma. By using the active nitride species, the nitridation of an Si film on a wafer can be accelerated even under low temperature conditions. However, if the Si film is nitrided using the nitriding agent in a plasma state, the chemical resistance of the formed SiN film deteriorates. Specifically, the SiN film is easily etched by a diluted hydrofluoric acid solution (hereinafter, referred to as a diluted HF solution). Therefore, a method is used in which a silicon carbonitride film (hereinafter, referred to as an SiCN film) is formed by adding carbon (C) to an SiN film to improve the chemical resistance of the SiCN film as compared with the SiN film.
In this method, as an SiC film is nitrided using active nitride species produced using plasma, the SiCN film is formed. For this reason, although the film forming temperature is lowered to a temperature zone of less than 630 degrees C., it is possible to obtain a sufficient film forming rate that can be actually used. However, if there is a microstructure having steps on a surface to be processed of a wafer, for example, a trench, it is difficult to form a film on a sidewall of a lower portion of the trench. This is because active nitride species, for example, ammonia radicals or the like, contact the sidewall of the trench and are then deactivated, so that active ammonia radicals do not make sufficient contact with the lower portion of the trench.
In this regard, a method of nitriding an SiC film without using plasma is used. Accordingly, it is possible to obtain an advantage in that a film is easily formed on a lower portion of a trench as compared with the conventional method.
However, the SiC film is nitrided without using plasma in this method. Thus, if the film forming temperature is lowered, for example, to a temperature zone of less than 630 degrees C., the film forming rate is rapidly reduced as compared with the case using plasma.